1. Field of the Invention
The invention relates to the packaging of liquid to paste substances in a flexible tube above which a rigid end cap is fitted, the said tube having a head comprising a flexible skirt connected through a shoulder to an approximately cylindrical neck, the said rigid end cap being designed to be fixed irreversibly to the head of the said tube.
2. Description of the Prior Art
The distribution end of most flexible tubes terminates with a neck delimiting a distribution channel and provided with an external thread on which a removable cap will be fitted. These plugs are usually small and have at least two disadvantages: firstly, they are easily lost by users and secondly it is difficult to hold the tube with head downwards in a stable manner, in a vertical position to make the tube look attractive and to facilitate gripping which is particularly appreciated by consumers.
This is why it is known how to replace these caps with larger diameter and stiffer caps fixed on one end of the tube. This greater stiffness can be achieved by increasing the thicknesses of the different parts forming the head, but this would increase the cost of the tube and its weight. This is why it is preferred to use a more rigid plastic material for plastic tubes. But in this case, the incompatibility in melting of the plastic from which the flexible skirt is made and the plastic that increases the stiffness of the end of the tube makes it preferable to mould the flexible tube and the said end (that we will call the “rigid end” in the remainder of this presentation) separately, and consequently the rigid end must subsequently be fixed reversibly on the head (which is more flexible) of the flexible tube.
The rigid end cap may be of several different natures: a simple rigid end cap base keeping the tube with the head facing downwards stable in the vertical position (“standup” tube) and a closing device called a service capsule, comprising a part that will be fixed on the neck of the tube (called the bottom) and a moving part called the cap, that pivots about a hinge attached to the said base and comprising means of closing off the distribution channel.
The attachment of this rigid end cap to the head of the flexible tube must be made in an economically satisfactory manner under high speed manufacturing conditions, in other words at a speed of the order of one or several hundred tubes per minute. For example, French patent application FR 2 650 253 issued by the applicant presents a rigid end cap and a tube with a neck, both being fitted with matching irreversible securing means; the neck is force fitted between two skirts attached to the bottom of the rigid end cap: a sealing skirt entering the inside of the neck and a skirt provided with securing means comprising engraving ribs and a click fit rim. This document recommends that three steps should be adopted in order to limit the forces necessary for attachment. These three steps are insertion of the sealing skirt into the orifice, etching of the ribs on the outside surface of the neck, and then click fitting.
When the rigid end caps are service capsules, the industrial attachment onto the head of the tube also causes a problem of orientation of the hinge with respect to the printed decor on the skirt and the end seam (called the terminal seam). Patent application FR 2 707 256 issued by the applicant proposes a solution for solving this orientation problem. It describes a capsule and a receptacle fitted with a neck, the capsule and the neck being provided with the means cooperating with each other to create an irreversible attachment; the neck is force fitted between two central skirts of the capsule, a sealing skirt entering the inside of the neck and a skirt provided with click fit rims for longitudinal locking. Rotational locking is achieved by trapping a flexible axial strip free to move radially between two profiled portions. The flexible strip is attached to the capsule and the profiled portions are attached to the top of the shoulder, close to the bottom of the neck.
FR 2 650 253 and FR 2 707 256 present high performance systems for the attachment of a rigid end cap to a flexible tube head. However, sealing at the contact between the sealing skirt of the rigid end cap and the internal wall of the neck can only be achieved if the inside diameter of the neck is sufficiently small compared with its outside diameter. It is observed that if the opening of the neck is large compared with the outside diameter of the neck, a force imposed on the shoulder of the tube, particularly at the junction between the shoulder and the skirt, would cause ovaling of the neck, and consequently its attachment to the sealing skirt of the rigid end cap is not leak tight. Therefore, this limits possibilities of use of rigid end caps fixed on flexible tubes, particularly when a multiple distribution orifice or an offset orifice is necessary, these two cases making it necessary to have a tube for which the diameter of the neck is large compared with the diameter of the flexible skirt.
Therefore, the applicant wanted to develop a flexible tube and rigid end cap assembly that could be fixed onto the said tube with a leak tight joint under economically satisfactory high speed industrial conditions, the said tube having a head comprising a neck continuing from a shoulder and the neck is approximately cylindrical with a large diameter, in other words larger than the diameter of the skirt.